In a meeting of musical minds that took just 48 hours to record, meticulous sonic sculptors Tortoise collaborated with the Ex, a group of Dutch avant noise-mongers. The result is In the Fishtank, a six-song EP that sometimes blends the bands' divergent styles into a harmonious hybrid, and other times falls victim to stylistic clashes. The more spacious tracks, like "Pleasure as Usual," "Huge Hidden Spaces" and especially "The Lawn of the Limp" feature the blend of dissonance and ambience, and highlight the best qualities of each of the collaborators. The slightly more fractured and fractious "Did You Comb?" is still a fairly accessible mix of the groups' visions, but the Ex-dominant "Central Heating" is a noisy, acquired taste. Spontaneous and mercurial, In the Fishtank truly is experimental rock -- but not all the experiments succeed completely.